Device for connecting bars end-to-end

ABSTRACT

A device for connecting bars end-to-end includes a hollow body having an internal cavity with at least one bar insertion opening and a longitudinal axis extending through the at least one insertion opening, and a plurality of radially adjustable clamping elements. The device further includes at least one locking element movably arranged inside the hollow body. The internal cavity of the hollow body has at least one slope inclined relative to the longitudinal axis of the hollow body. The at least one locking element has an inclined face that matches the profile of the at least one slope and a gripping face with at least one protrusion.

CROSS-REFERENCE TO RELATED U.S. APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

REFERENCE TO AN APPENDIX SUBMITTED ON COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device for connecting two bars in anend-to-end relationship. The device has a particular application incoupling the ends of reinforcing bars used in structural concrete.

2. Description of Related Art

Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.

In the art of joining two bars end-to-end in order to extend theircontinuity, it is known to use a tubular sleeve that receives the endportion of each bar, the sleeve having radially-oriented elements thatare forced into the material of the bars in order to lock them.According to one device as disclosed in U.S. Pat. No. 5,046,878 issuedto Young on Sep. 10, 1991, the radially oriented elements are providedas screws and racks that are arranged longitudinally along the sleeve.

The prior art systems have drawbacks. First of all, the pneumatic andelectric tools that are commonly available on the market are of limitedcapacity, which means that it is not possible to increase the size orstrength of the screws beyond a certain limit. The connection of largeror stronger bars is therefore not possible. Secondly, the effortgenerated by torquing the screws serves to press the racks into thesleeve as much as to press them into the bars. Less than half of thetightening effort is thus available to actually clamp the bars. Finally,its performance under a tensile load is very difficult to maintain andto control. Indeed, the effectiveness of the fitting of the sleeve ontothe bar end wholly depends on the torque applied on the screws, which isthe torque at which the screw heads shear off.

These screws have their neck reduced so that the shearing occurs outsidetheir threaded area. The precision of this diameter reduction, as wellas the radius at the bottom of the reduction, are difficult to achieve.The stress riser at the reduction may vary from 1 to 4, depending on theradius at the bottom of the reduction, which on top of being difficultto produce accurately, is also difficult to measure and control. Thisvariation in stress riser affects directly the torque at which thescrews shear off, and consequently the performance of the system.

Moreover, the screws are calculated to shear off under a purely torsioneffort. In practice however, it cannot be guaranteed that the pneumaticor electric wrench or screwdriver is perfectly aligned on the axis ofthe screw. Because this tool is manually held, a certain angle betweenits axis and that of the screw is unavoidable. Such an angle adds aflexural effort to the torsion effect, thereby reducing the torquenecessary to shear off the screws, and hence reducing the systemperformance.

Also known are prior art devices disclosed in U.S. Pat. No. 5,909,980and U.S. Pat. No. 6,202,282 that work essentially in the same way as thepreviously referenced device. These prior art systems replace thegripping effect of the racks by the friction effect of the bar againstthe internal surface of the sleeve. Because friction is not as efficientas gripping in transmitting effort, it compensates by using a longerlength and a larger number of screws. Being so closely related to theother prior art cited, these other prior art systems do not bring anyparticular additional benefit, while still suffering from the samedisadvantage and the additional drawback of bulkiness.

Also known is a device as disclosed in U.S. Patent Publication No.2004/0238558 that also works essentially in the same way as thepreviously cited prior art systems. This particular prior art systemprovides two rows of screws and uses an internal thread rather thanracks to produce the gripping effect inside the sleeve. Being so closelyrelated to the other prior art cited, this prior art system does notbring any additional benefits, while still suffering from the samedisadvantages and the additional drawback that the angle between the tworows of screws requires extra free space for installation.

BRIEF SUMMARY OF THE INVENTION

Compared to many of the existing systems to connect two bars end-to-end,such as threading or forging the bar ends, the device of the presentinvention presents the advantage of not needing any preparation of thebar end. This means that it is not necessary to either transport thebars to a workshop where their ends can be prepared, or transport to thelocation of the bars the machinery needed to prepare their ends. Thissystem was indeed developed with the aim of enabling a site assembly,with only a pneumatic or electric wrench needed to torque the screws. Asite assembly is a great benefit in some industries such as theconstruction or the oil industry. It is also a great benefit in largecountries where transport of bars is an issue, due to long distances.

It is an object of the present invention to provide a device forconnecting bars in an end-to-end relationship that upholds the benefitof site assembly, in addition to new benefits in terms of increasedreliability, improved safety to the structure, and better tensile andload bearing performance.

The present invention also reduces bulkiness compared to the prior artsystems. The improved size of the device improves safety for theinstaller and the individuals working around the device at the work orconstruction site.

The present invention is a device for connecting bars end-to-endcomprising a hollow casing or body whose internal cavity presentsslopes, or surfaces that are at a certain angle relative to the axis ofthe bars to be connected.

According to the present invention, the device further comprises atleast one locking element movably arranged inside the hollow body. Theinternal cavity of the body comprises at least one slope, that isinclined relative to the longitudinal axis of the body. The lockingelement also has an inclined face that matches the profile of at leastone slope of the internal cavity and a gripping face with at least oneprotrusion. With this structure, the device according to the presentinvention achieves a self-locking effect in which the clamping andgripping force of the device increases with increased loading of thebars to be connected. As a result, the device according to the inventionachieves a higher load bearing performance on an improved safety andreliability level. Moreover, thanks to a reduced bulkiness of thedevice, improved safety is provided to the installer and the peopleworking around the device on an industrial or construction site.

In the preferred embodiment, the hollow body has at least two insertionopenings and its internal cavity has at least two slopes. The slopes areinclined relative to the longitudinal axis of the hollow body, theseinclinations being in opposite directions. As a result, a plurality ofbars can be reliably connected in a self-locking manner. If part of thedevice is to be welded to a steel structure, it can be adapted toreceive one bar only. Then, the hollow body has only one insertionopening, and its internal cavity has only one slope.

The shape of the slopes and inclined faces is not particularly limitedin the present invention, as long as cooperating slopes and inclinedfaces match each other.

The slopes may be flat or curved.

In order to achieve an optimum gripping force and an easy and reliableoperation of the device, it is preferred that the gripping surface isgenerally parallel to the longitudinal axis of the hollow body. Thematerial of the gripping surface is chosen and its teeth are shaped tosuitably bite into the material of the bars to be connected.

According to a further development of the present invention, thecross-sectional area of the internal cavity of the hollow body is notregular but rather increases from a minimum at the extremity towards amaximum at the middle and then decreases back to a minimum at the otherextremity. Alternatively, the cross-sectional area of the internalcavity may also decrease from a maximum at the extremity towards aminimum at the middle and then increase back to a maximum at the otherextremity. This allows an easy manufacture and a stable construction ofa hollow body having slopes in its internal cavity.

The shape and type of the radially-adjustable clamping elements are notspecifically restricted in the present invention. In many cases, thesewill be screws which may have pointed or flat ends, depending on thematerial of the bars to be connected. They may have standard necks orneck reductions designed to shear under a certain torque.

There may be provided one or more rows of screws.

In order to achieve a proper and easy positioning of the bars/bar endsto be connected, it is preferred that stop means are provided in theinternal cavity of the body.

In order to increase the variability of the device, the locking elementsare of different radial thickness in order to accommodate bars ofdifferent sizes.

The locking elements may in the present invention act as “passive”locking elements which develop a “self-locking effect” only after anincrease load has been brought on the bars to be connected. However, inorder to reduce possible slip or deformation, the device according tothe present invention further comprises a pushing means for pushing thelocking elements from outside of the hollow body. In this way, thelocking elements may be prestressed and/or it can be avoided duringfastening the radially-adjustable clamping elements that the at leastone locking element(s) slides away.

According to a further development of the present invention, at leastone internal phase of the body comprises ribs or grooves. This willimprove the bond and anchoring of the device when used in concrete orthe like.

Further, in order to increase the durability of the device according tothe present invention, a corrosion-protection or binding substance ispoured or injected inside the body.

According to a further aspect, the present invention provides a methodof connecting bars end-to-end using the device as described above.Further details on the method of connecting bar ends according to thepresent invention will be apparent from the following detaileddescription.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a perspective view of a device for connecting bar endsaccording to a first embodiment of the present invention.

FIG. 2 shows a cross-sectional view of the embodiment shown in FIG. 1.

FIG. 3 shows a cross-sectional view of a variant of the first embodimentwhere a corrosion-protection or binding substance has been injectedinside the body.

FIG. 4 shows a perspective view of a device for connecting bar endsaccording to a second embodiment of the present invention.

FIG. 5 shows a perspective view of a device for connecting bar endsaccording to a third embodiment of the present invention.

FIG. 6 shows a cross-sectional view of the device for connecting barends according to a further embodiment of the present invention.

FIG. 7 a to 7 f show perspective views of various locking elements.

FIG. 8 shows a cross-sectional view of a device for connecting barsend-to-end according to a fourth embodiment of the present inventionadapted to connect bars of different diameters.

FIG. 9 shows a cross-sectional view of a device for connecting barsend-to-end according to a fifth embodiment of the present inventionprovided with a pushing means.

FIG. 10 shows a cross-sectional view of a device for connecting barsend-to-end according to a sixth embodiment of the present invention,also provided with a pushing means.

FIG. 11 shows a cross-sectional view of a device for connecting barsend-to-end according to a seventh embodiment of the present inventionadapted to receive mainly compressive forces.

FIG. 12 shows a cross-sectional view of a device for connecting barsend-to-end according to a seventh embodiment of the present inventionadapted to receive both tensile and compressive forces.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the invention are discussed in the followingwith reference to the enclosed drawings.

A device 1 for connecting the ends 2′ of a bar according to a firstembodiment of the present invention is schematically shown in aperspective view in FIG. 1 as well as in a cross-sectional view in FIG.2. The device is adapted for connecting rebars and the like end-to-endas they are used in construction, for instance, in reinforced concretestructures. The device 1 comprises a hollow body 10 having an internalcavity 12 which, in the present embodiment, comprises two insertionopenings 14 through which a longitudinal axis extends. The direction ofextension of the longitudinal axis coincides with the direction ofextension of the bars 2 to be connected (FIG. 2).

Furthermore, the device 1 comprises a plurality of clamping screws 16which are fitted into threaded holes formed in the hollow body 10. Thescrews may have a reduced neck so as to produce a defined failure. Ascan be seen in FIG. 2, the screws 16 are adapted to press on the bars 2inserted into the hollow body 10.

Further, the device 1 comprises two locking elements 18 which aremovably arranged inside the internal cavity 12 of the hollow body 10.Specifically, the internal cavity 12 of the body 10 comprises two slopes12′ which are inclined relative to the longitudinal axis of the body 10,and the locking elements 18 each comprise a inclined face 18′ whichmatches the profile of the corresponding slope 12′ and is in contacttherewith. In addition, each locking element 18 has a gripping face 18″having a plurality of rack teeth. The gripping face 18″ is adapted togrip and fix the respective bar 2 together with the screws 16.Therefore, it is preferred that the gripping faces 18″ are generallyparallel to the longitudinal axis of the bars 2 and body 10.

As can be seen in FIG. 2, the device 1 further comprises stop means 20,for example in the form of stop or separation walls. As shown in FIG. 6,this stop or separation wall 20 may also fully separate the internalcavity 12 in two parts.

For applications where the connection needs to grip or bond with anexternal surrounding material, for example in concrete construction,ribs or grooves 24 may be provided on the external surface of the body10.

The connection is achieved by inserting the ends 2′ of bars 2 until theyhit the wall 20. The screws 16 are then tightened either until a giventorque, or until their heads shear off, thereby forcing the ends 2′ ofbars 2 against the gripping face 18″ of the locking elements 18, andlocking themselves into the surface material of the bars 2.

The bars 2 are then put in use and sustain a tensile load. This tensileload tends to pull both bars apart, along with the locking elements 18thanks to the gripping achieved on their gripping faces 18″. When thelocking elements 18 move apart by sliding over the slopes 12′, theyforce their grip 18″ further into the material of the bars 2. Thus, theresistance of the device increases with the load applied on the bars.

FIG. 3 relates to a second embodiment for applications where it isnecessary to fill up the cavity 12 with a corrosion-protection orbinding substance, end caps 26 may be provided to close the spaces ateach extremity of the connection, and a hole 28 may be provided in thebody 10, through which the substance may be poured or injected.

FIGS. 4 and 5 show that the external shape of the hollow body 10 may bewidely varied within the present invention. Further, the device 1 maycomprise one row or also plural rows of screws 16, as shown in FIG. 5.

Also the shape of the locking elements 18 is not specifically limited inthe present invention. Various examples of suitable locking elements 18are shown in FIGS. 7A to 7G. For instance, the inclined face 18′ may beflat or curved just like the gripping face 18″. Of course, furtherdesigns are possible.

FIG. 8 shows an embodiment which is adapted to connecting bars 2 havingdifferent diameters. For this purpose, the locking elements 18 have adifferent radial thickness. Specifically, in FIG. 8, the locking element18 on the left hand side is adapted to grip a bar 2 having a smallerdiameter and, therefore, itself has a smaller radial thickness than thelocking element 18 on the right hand side.

FIGS. 9 and 10 show a sixth and seventh embodiment, respectively, withadditional pushing means 22 for pushing the locking elements 18 againstthe ends 2′ of bars 2 prior to the tightening of screws 16. This featureis illustrated in FIG. 9 with a cam 23 that is rotated around its axis.In FIG. 10 the pushing means 22 comprises a central screw 25 that pusheson the rear faces of the locking elements 18.

FIG. 11 schematically shows an eighth embodiment of the presentinvention for cases where the connection must withstand not tensile, butmainly compression efforts. In this embodiment, the slopes 12′ arediverging towards the insertion openings 14.

Under a compression effort, the locking elements 18 are moving towardsthe center of the body, thereby securing the clamping of the bars 2.

FIG. 12 schematically shows an ninth embodiment of the present inventionfor the cases where the connection must withstand alternate cyclictensile and compression efforts. In this embodiment, a total of fourlocking elements 18 a, 18 b are provided, namely two locking elements 18a, 18 b per bar 2. Further, the locking elements 18 a, 18 b of each barhave their respective slopes 18′ inclined in opposite directions. Thus,under a tensile effort, the locking elements 18 a are moving towards theextremities of the body, thereby securing the clamping of the bars.Under a compression effort, the locking elements 18 b are moving towardsthe center of the body, thereby securing the clamping of the bars.

The connection of the bars 2 is achieved by inserting the device loverthe end 2′ of a first bar 2, said bar end 2 being received by the cavity12 between the locking element 18 and the screws 16. A second bar 2 isthen inserted into the other side of the device 1. The device can now beoriented in the radial direction deemed most suitable either for accesspurpose or for space optimization. The pushing means 22 may then be usedto reduce the clearance between the bars 2 and the device 1. The screws16 are finally torqued so that they press the bar 2 against the lockingelements 18 and themselves penetrate into the surface of the bars 2.

When the bars 2 are pulled by application of a tensile load, the initialresistance comes from the gripping effect between the screws 16 and thelocking elements 18. As the load increases, the locking elements 18 movealong the slopes 12′ of the body 10, and further lock the bar ends 2′inside the cavity, thereby greatly improving the tensile performance:the stronger the pull on the bars, the stronger the lock.

1. A device for connecting bars end-to-end, said device comprising: ahollow body having an internal cavity with at least one bar insertionopening and a longitudinal axis extending through said at least oneinsertion opening, said internal cavity having at least one slopeinclined relative to a longitudinal axis of said hollow body; aplurality of radially-adjustable clamping elements mounted on saidhollow body; and at least one locking element movably arranged insidesaid hollow body, said at least one locking element having an inclinedface matching said at least one slope of said internal cavity and agripping face having at least one protrusion.
 2. The device according toclaim 1, wherein said internal cavity of said hollow body has at leasttwo slopes inclined relative to the longitudinal axis of said hollowbody, said at least two slopes being inclined in opposite directions. 3.The device according to claim 1, wherein said gripping face is generallyparallel to the longitudinal axis of said hollow body.
 4. The deviceaccording to claim 1, wherein said internal cavity of said hollow bodyhas a cross-section area increasing from a minimum at one end of saidinternal cavity to a maximum at a middle of said internal cavity anddecreasing from said maximum at said middle of said internal cavity to aminimum at an opposite end of said internal cavity.
 5. The deviceaccording to claim 1, wherein said internal cavity of said hollow bodyhas a cross-section area decreasing from a maximum at one end of saidinternal cavity to a minimum at a middle of said internal cavity andincreasing from said minimum at said middle of said internal cavity to amaximum at an opposite end of said internal cavity.
 6. The deviceaccording to claim 1, wherein said radially-adjustable clamping elementshave a designated preferential location of failure.
 7. The deviceaccording to claim 1, further comprising: stop means provided in saidinternal cavity of said hollow body.
 8. The device according to claim 2,wherein said at least one locking element has a radial thicknesses toaccommodate bars of different sizes.
 9. The device according to claim 1,further comprising: pushing means for pushing said at least one lockingelement from outside of said hollow body.
 10. The device according toclaim 1, wherein said at least one locking element having an endchamfered in order to reduce maximum height thereof.
 11. The deviceaccording to claim 1, wherein said hollow body has at least one externalface being comprised of ribs or grooves.
 12. The device according toclaim 1, further comprising: a corrosion-protection substance poured orinjected inside said hollow body.
 13. The device according to claim 1,further comprising: a binding substance poured or injected inside saidhollow body.
 14. A method of connecting bars end-to-end, said methodcomprising: inserting bars into a device comprised of a hollow bodyhaving an internal cavity with at least one bar insertion opening and alongitudinal axis extending through said at least one insertion opening,said internal cavity having at least one slope inclined relative to alongitudinal axis of said hollow body; a plurality ofradially-adjustable clamping elements mounted on said hollow body; atleast one locking element movably arranged inside said hollow body, saidat least one locking element having an inclined face matching said atleast one slope of said internal cavity and a gripping face having atleast one protrusion; and stop means provided in said internal cavity ofsaid hollow body, said bars being inserted until contacting said stopmeans; and tightening said radially-adjustable clamping elements untilends of said bars are forced against said gripping face, saidradially-adjustable clamping elements being locked into a surfacematerial of said bars, said at least one locking element being furtherforced against said bars when said bars are subjected to a tensile load.